In a liquid crystal display device, in order to realize high reliability of the image quality uniformity, life span, or the like of a liquid crystal panel, a cooling technique is used which satisfies temperature standards to guarantee the operation of a light source part, a control part, and a power supply part.
For this purpose, generally, a technique is used for providing an air intake port and an exhaust port, which introduce surrounding low-temperature air, in a liquid crystal display device, and introducing the low-temperature air to cool a light source part, a control part, and a power supply part which are mounted in the liquid crystal display device.
In this technique, however, dust including non-conductive and conductive substances which are scattered in ambient air enters a liquid crystal display device which is installed in public places, such as the partially outdoor areas, from the intake port provided in the liquid crystal display device. The dust builds up on the light source part, control part, and power supply part inside the liquid crystal display device.
Particularly, when dust including conductive substances has entered the inside of the liquid crystal display device, short circuiting may occur between electronic circuit parts mounted in the liquid crystal display device, may hinder reliability, and cause a problem in terms of the quality of the product.
For this reason, the conventional technique cannot be said to be satisfactory in terms of dust resistance and cooling performance in regard to a liquid crystal display device to be installed in public places, such as the partially outdoor areas.
A technique regarding a liquid crystal display device and a cooling method of a lamp part of the liquid crystal display device is disclosed in Patent Document 1. This technique includes a housing part which houses a dust resistant fluorescent lamp of the liquid crystal display device, and a cooling mechanism which introduces air heated by the fluorescent lamp from the housing part, then cools the air, and returns the cooled air to the housing part, as a device having a cooling mechanism in a back light part. Therefore, some effects are exhibited as a configuration which has dust resistance, cooling performance and prevention of dust entering from ambient air in the sealed fluorescent lamp part.
However, in recent years, the power consumption of a back light serving as a light source part and an electric power supply part have tended to increase due to the progress of the improvement in the quality of the product due to increases in the screen size and luminance of the liquid crystal display device.
Additionally, an audio function and a personal computer function are also included, and the product performance has also improved. Along with this, the power consumption of the whole liquid crystal display device is increasing.
Moreover, there is a remarkable relationship between the life span and temperature of the liquid crystal panel. For example, in a case where the installation environment temperature in the partially outdoor areas in summer is 40° C., the temperature of the liquid crystal panel should be less than or equal to 55° C. including a design margin.
In addition, in the installation conditions in the partially outdoor areas mentioned above, in order to prevent the entrance of dust which is scattered in ambient air and to obtain high reliability, it is desired that the liquid crystal display device itself has dust resistance, and a cooling part which satisfies the temperature standards is included.
Additionally, the slimming, weight saving, and cost reduction of a large screen liquid crystal display device are desired, and a heat problem accompanying dust resistance and cooling performance becomes more serious than in the past.
In such a technical background, in the cooling method of the lamp part of the liquid crystal display device disclosed in Patent Document 1, the cooling part of the fluorescent lamp part with dust resistance is provided with communication holes in the fluorescent lamp and two U-shaped ducts, and cools only the heat generated from the fluorescent lamp by circulating air within the ducts by an air blowing part.
However, according to the ratio of amount of heat in the recent whole liquid crystal display device mentioned above, the amount of heat generated from the fluorescent lamp, and a light source portion of an inverter circuit is about 60%. Additionally, the amount of heat generated from electronic circuit parts mounted in an audio function, a personal computer function, an electric power supply part, or the like is about 40%.
Accordingly, with regard to other audio functions, personal computer functions, and electric power supply parts, the sealing performance of preventing the entrance of dust which is scattered in ambient air and the cooling performance and high reliability which satisfy the temperature standards of all mounted parts at an installation environment temperature of 40° C. cannot be secured only by the cooling part of the fluorescent lamp part.
Patent Document 1: Japanese Patent No. 3975506